Subject: Re: [RFC PATCH v4 7/13] memory-hotplug : remove_memory calls __remove_pages

From: Yasuaki Ishimatsu <[email-masked]>
Date: Thu, 19 Jul 2012 18:30:19 +0900

Hi Bob,

2012/07/19 17:32, Bob Liu wrote:
> On Wed, Jul 18, 2012 at 6:12 PM, Yasuaki Ishimatsu
> <[email-masked]> wrote:
>> The patch adds __remove_pages() to remove_memory(). Then the range of
>> phys_start_pfn argument and nr_pages argument in __remove_pagse() may
>> have different zone. So zone argument is removed from __remove_pages()
>> and __remove_pages() caluculates zone in each section.
>>
>> When CONFIG_SPARSEMEM_VMEMMAP is defined, there is no way to remove a memmap.
>> So __remove_section only calls unregister_memory_section().
>>
>> CC: David Rientjes <[email-masked]>
>> CC: Jiang Liu <[email-masked]>
>> CC: Len Brown <[email-masked]>
>> CC: Benjamin Herrenschmidt <[email-masked]>
>> CC: Paul Mackerras <[email-masked]>
>> CC: Christoph Lameter <[email-masked]>
>> Cc: Minchan Kim <[email-masked]>
>> CC: Andrew Morton <[email-masked]>
>> CC: KOSAKI Motohiro <[email-masked]>
>> CC: Wen Congyang <[email-masked]>
>> Signed-off-by: Yasuaki Ishimatsu <[email-masked]>
>>
>> ---
>>   arch/powerpc/platforms/pseries/hotplug-memory.c |    5 +----
>>   include/linux/memory_hotplug.h                  |    3 +--
>>   mm/memory_hotplug.c                             |   19 ++++++++++++-------
>>   3 files changed, 14 insertions(+), 13 deletions(-)
>>
>> Index: linux-3.5-rc6/mm/memory_hotplug.c
>> ===================================================================
>> --- linux-3.5-rc6.orig/mm/memory_hotplug.c      2012-07-18 18:00:27.440145432 +0900
>> +++ linux-3.5-rc6/mm/memory_hotplug.c   2012-07-18 18:01:02.070712487 +0900
>> @@ -275,11 +275,14 @@ static int __meminit __add_section(int n
>>   #ifdef CONFIG_SPARSEMEM_VMEMMAP
>>   static int __remove_section(struct zone *zone, struct mem_section *ms)
>>   {
>> -       /*
>> -        * XXX: Freeing memmap with vmemmap is not implement yet.
>> -        *      This should be removed later.
>> -        */
>> -       return -EBUSY;
>> +       int ret = -EINVAL;
>> +
>> +       if (!valid_section(ms))
>> +               return ret;
>> +
>> +       ret = unregister_memory_section(ms);
>> +
>
> I saw a patch from Jiang Liu "mm/hotplug: free zone->pageset when a
> zone becomes empty" to
> free the zone->pageset and i think there may more cleanup needed when
> a zone becomes empty.
>
> We already have __add_zone() in __add_section(), what about add a
> function like __remove_zone()
> to do the cleanup here?

Thank you for your cooment. As you say, I think cleanup function of zone
is necessary. So I'll update it.

Thanks,
Yasuaki Ishimatsu.

>
>> +       return ret;
>>   }
>>   #else
>>   static int __remove_section(struct zone *zone, struct mem_section *ms)
>> @@ -346,11 +349,11 @@ EXPORT_SYMBOL_GPL(__add_pages);
>>    * sure that pages are marked reserved and zones are adjust properly by
>>    * calling offline_pages().
>>    */
>> -int __remove_pages(struct zone *zone, unsigned long phys_start_pfn,
>> -                unsigned long nr_pages)
>> +int __remove_pages(unsigned long phys_start_pfn, unsigned long nr_pages)
>>   {
>>          unsigned long i, ret = 0;
>>          int sections_to_remove;
>> +       struct zone *zone;
>>
>>          /*
>>           * We can only remove entire sections
>> @@ -363,6 +366,7 @@ int __remove_pages(struct zone *zone, un
>>          sections_to_remove = nr_pages / PAGES_PER_SECTION;
>>          for (i = 0; i < sections_to_remove; i++) {
>>                  unsigned long pfn = phys_start_pfn + i*PAGES_PER_SECTION;
>> +               zone = page_zone(pfn_to_page(pfn));
>>                  ret = __remove_section(zone, __pfn_to_section(pfn));
>>                  if (ret)
>>                          break;
>> @@ -1031,6 +1035,7 @@ int __ref remove_memory(int nid, u64 sta
>>          /* remove memmap entry */
>>          firmware_map_remove(start, start + size, "System RAM");
>>
>> +       __remove_pages(start >> PAGE_SHIFT, size >> PAGE_SHIFT);
>>   out:
>>          unlock_memory_hotplug();
>>          return ret;
>> Index: linux-3.5-rc6/include/linux/memory_hotplug.h
>> ===================================================================
>> --- linux-3.5-rc6.orig/include/linux/memory_hotplug.h   2012-07-18 18:00:27.445145371 +0900
>> +++ linux-3.5-rc6/include/linux/memory_hotplug.h        2012-07-18 18:00:40.461982690 +0900
>> @@ -89,8 +89,7 @@ extern bool is_pageblock_removable_noloc
>>   /* reasonably generic interface to expand the physical pages in a zone  */
>>   extern int __add_pages(int nid, struct zone *zone, unsigned long start_pfn,
>>          unsigned long nr_pages);
>> -extern int __remove_pages(struct zone *zone, unsigned long start_pfn,
>> -       unsigned long nr_pages);
>> +extern int __remove_pages(unsigned long start_pfn, unsigned long nr_pages);
>>
>>   #ifdef CONFIG_NUMA
>>   extern int memory_add_physaddr_to_nid(u64 start);
>> Index: linux-3.5-rc6/arch/powerpc/platforms/pseries/hotplug-memory.c
>> ===================================================================
>> --- linux-3.5-rc6.orig/arch/powerpc/platforms/pseries/hotplug-memory.c  2012-07-18 18:00:27.442145407 +0900
>> +++ linux-3.5-rc6/arch/powerpc/platforms/pseries/hotplug-memory.c       2012-07-18 18:00:40.470982578 +0900
>> @@ -76,7 +76,6 @@ unsigned long memory_block_size_bytes(vo
>>   static int pseries_remove_memblock(unsigned long base, unsigned int memblock_size)
>>   {
>>          unsigned long start, start_pfn;
>> -       struct zone *zone;
>>          int i, ret;
>>          int sections_to_remove;
>>
>> @@ -87,8 +86,6 @@ static int pseries_remove_memblock(unsig
>>                  return 0;
>>          }
>>
>> -       zone = page_zone(pfn_to_page(start_pfn));
>> -
>>          /*
>>           * Remove section mappings and sysfs entries for the
>>           * section of the memory we are removing.
>> @@ -101,7 +98,7 @@ static int pseries_remove_memblock(unsig
>>          sections_to_remove = (memblock_size >> PAGE_SHIFT) / PAGES_PER_SECTION;
>>          for (i = 0; i < sections_to_remove; i++) {
>>                  unsigned long pfn = start_pfn + i * PAGES_PER_SECTION;
>> -               ret = __remove_pages(zone, start_pfn,  PAGES_PER_SECTION);
>> +               ret = __remove_pages(start_pfn,  PAGES_PER_SECTION);
>>                  if (ret)
>>                          return ret;
>>          }
>>
>> --
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